#include <stdio.h>
#include <math.h>                      //1                     
int main()
{	   		 	   	
    float a, b, c;
    float s, area;

    printf("Input a,b,c:\n");
    scanf("%f,%f,%f", &a, &b, &c);      //1

    if ( (a + b) > c && (a + c) > b && (b + c) > a ) //2
    {	   		 	   	
        s = (float) 1.0 / 2 * (a + b + c);      //1
        area = (float) sqrt(s * (s - a) * (s - b) * (s - c)); //1
        printf("area=%.2f\n", area);     //1
    }
    else       //1
        printf("No triangle!\n");

    return 0;
}